Dinosaur-killing asteroid triggered a global firestorm

Chicxulub crater NASA earth observatory
The Chicxulub Crater on the Yucatan Peninusla, where an asteroid impact 66 million years ago led to the extinction of most life on Earth. Learn more at this NASA Earth Observatory website.

CU Boulder study suggests fallout from collision super-heated the sky to broil the Earth’s surface

By Summit Voice

SUMMIT COUNTY — A giant asteroid that rammed Earth and killed of the dinosaurs may have broiled the entire surface of the planet by super-heating the atmosphere, according to a new study by CU Boulder scientists.

Using computer models to simulate the collision, the researchers with the Cooperative Institute for Research in Environmental Sciences said the blast vaporized huge amounts of rock that were blown high above Earth’s atmosphere.

The re-entering  material would have heated the upper atmosphere enough to glow red for several hours at roughly 2,700 degrees Fahrenheit — about the temperature of an oven broiler element and hot enough to trigger a global firestorm that would have burned every twig, bush and tree on Earth, killing any organism not sheltered underground or underwater.

Previous studies have also suggested that the asteroid, which hit in the area of present-day Mexico, started massive fires, but scientists have always been puzzled why there is little charcoal found at the geologic boundary between the Cretacous and the Paleogene eras.

So the CU-led team developed an alternate explanation after finding that similar studies had corrected their data for changing sedimentation rates. When the charcoal data were corrected for the same changing sedimentation rates they show an excess of charcoal, not a deficiency, said CIRES researcher Douglas Robertson.


“Our data show the conditions back then are consistent with widespread fires across the planet,” said Robertson. “Those conditions resulted in 100 percent extinction rates for about 80 percent of all life on Earth,” he said.

There was enough infrared radiation from the upper atmosphere to create searing conditions that likely ignited tinder, including dead leaves and pine needles. If a person was on Earth back then, it would have been like sitting in a broiler oven for two or three hours, Robertson said.

The amount of energy created by the infrared radiation the day of the asteroid-Earth collision is mind-boggling.

“It’s likely that the total amount of infrared heat was equal to a 1 megaton bomb exploding every four miles over the entire Earth,” he said.

A 1-megaton hydrogen bomb has about the same explosive power as 80 Hiroshima-type nuclear bombs, he said. The asteroid-Earth collision is thought to have generated about 100 million megatons of energy, said Robertson.

Some researchers have suggested that a layer of soot found at the K-Pg boundary layer roughly 66 million years ago was created by the impact itself. But Robertson and his colleagues calculated that the amount of soot was too high to have been created during the massive impact event and was consistent with the amount that would be expected from global fires.

A paper on the subject was published online this week in the Journal of Geophysical Research-Biogeosciences, a publication of the American Geophysical Union. Co-authors on the study include CIRES Interim Director William Lewis, CU Professor Brian Toon of the atmospheric and oceanic sciences department and the Laboratory for Atmospheric and Space Physics and Peter Sheehan of the Milwaukee Public Museum in Wisconsin.


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